The problem of designing a saturated output-feedback controller to stabilize a class of continuous three-state bioreactors with Haldane inhibited kinetics is addressed. The reactor must be maintained about the (locally stable but possibly structurally unstable) steady-state with maximum production rate by manipulating the substrate feed rate on the basis of a biomass measurement. The consideration of the problem in the light of bioreactor (bifurcation and invariant set) dynamical and (passivity and observability) structural characteristics leads to a saturated linear dynamic OF control design with: (i) PI scheme with observer-based antiwindup protection, (ii) simple construction and tuning, and (iii) closed-loop robust stability conditions in terms of control gains and limits. The PI controller recovers (up to observer convergence and saturation) the behavior of a model-based nonlinear state-feedback passive stabilizing controller equivalent to an exact nonlinear model-based predictive controller with infinite-time receding horizon. The proposed approach is illustrated with a representative case example through numerical simulations. (C) 2013 Published by Elsevier Ltd.